In order to spare some I/O operations, be more intelligent about when to
read from the PHY.

Pointed out by Bogdan Costescu.
Signed-off-by: NTommy S. Christensen <tommy.christensen@tpack.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>